If you live in New York and were on Twitter about an hour ago, something like this probably happened to you: you read a tweet about an earthquake from someone in DC. Then, moments later, you felt it. Here's why.

Basically, as XKCD explained some time back, the fiber signals that usher your beeps and bops over the internet move at a much, much faster rate than seismic waves. Which means that your quake-related texts, tweets, and emails can sprint to their targets faster than the quake itself, assuming your missives are traveling more than 100km.

Whether that gives you enough time to find the nearest shelter, well, that depends on how long you take to RT. [xkcd via @Baratunde]